Pneumatic pressure reducing valve with rapid discharge

ABSTRACT

A pressure reducing valve has a plunger having an axial hole, which plunger is movable in a valve body between two extreme positions defined by stops and under the action of resilient means. A stem valve is movable in the axial hole and is adapted to assume a stop position such that it closes the axial hole when the plunger is in a rest position and that it leaves the hole open when the plunger is in the other positions. A control aperture admits a control pressure to a reaction surface on the plunger in order to produce a regulable increase in the resistance offered by the resilient means to the movement of the plunger.

United States Patent 1 3,702,622 Michellone [4 1 Nov. 14, 1972 [54]PNEUMATIC PRESSURE REDUCING 3,228,731 l/ 1966 Valentine 137/102 X VALVEWITH RAPID DISCHARGE 3,275,009 9/1966 Frania et a1 ..l37/l07 X [72]Inventor: Giancarlo Michellone, Strada delle Primary Examiner M y NelsonC ll,C b ,Ital ampere 8 am lane y Assistant ExaminerDav1d J. ZobkrwFiled! J 1971 Att0rney-Sughrue, Rothwell, Mion, Zinn & Macpeak [21]Appl. No.: 110,230

[57] ABSTRACT [30] Foreign Application priority Dam Apressure reducingvalve has a plunger having an axial hole, which plunger IS movable in avalve body Feb. 3, 1970 Italy ..67329 A/7O between two extreme positionsd fi by stops and under the action of resilient means. A stern valve is[52] US. Cl. "137/107, 303/22 A movable in the axial hole and is adaptedto assume a [51] Int. Cl. ..B60t 8/18, G05d 7/00 Stop position Such thatit closes the axial hole when [58] FIG! 0 Search I07, A the p g is arest position and that it leaves the v hole open when the plunger is inthe other positions. [56] Reterences cued A control aperture admits acontrol pressure to a reac- UNITED STATES PATENTS tion surface onplunger in order to produce a g regulabl increase in the resistanceoffered by the 2,858,840 1 l/ 1958 Wright 1 37/107 X resilient means tohe movement f the plunger 2,406,284 8/1946 Fitch ..l37/l02 3,022,1 l8 2/1962 Dobrikin l 102 X 1 Claim, 2 Drawing Figures Hi 19 20 1e 20 19 a l Pl 31 27 I i 33 11a 13 13 11 1o 15 l I l a 30 1, 31 l /21 l w 129 24 25as i 25 24 PAIENIEMMM 1 3.702.622

SHEET 1 [IF 2 |11a 13 16 I I u! HI INVENTOR GIANCARLO MIC'HELLONE suzknu'VWM, M

BY xu d ATTORNEYS PMENTED m 1 4 m2 SHEET 2 [IF 2 PNEUMATIC PRESSUREREDUCING VALVE WITH RAPID DISCHARGE The present invention relates to apneumatic pressure reducing valve with rapid discharge, of which thereduction ratio is controllable by means of another pneumatic pressure.

It is to be noted that the present invention can be used moreparticularly but not exclusively in braking installations which applybraking correction and/or prevent the wheels of the vehicle fromskidding.

Recent developments in vehicle braking installations which prevent thewheels from skidding, or anti-skid braking installations, which latterexpression will be used hereinafter, have led to a need for valves, moreparticularly pneumatic valves, which are adapted to be controlled bymeans of a control pressure.

A main object of the present invention is therefore to provide apneumatic pressure reducing valve with rapid discharge, in which it ispossible to control the reduction ratio between the inlet and outletpressures by means of a further pneumatic control pressure.

A further object of the invention is to provide a valve of the aforesaidtype which is of relatively simple structure and moderate cost. I

A further object of the invention is to provide a valve of the aforesaidtype which offers maximum certainty of satisfactory operation, so thatit can be used in antiskid braking installations. The invention achievesthe aforesaid and other objects and advantages with a pressure reducingvalve controllable by means of a control pressure, characterized in thatit comprises a. a plunger having an axial hole and movable in a valvebody between two extreme positions defined by stops and by the action ofresilient resisting means.

b. a valve having a stem and movable in the axial hole of the plungerand adapted to assume a stop position such that the said stern valvecloses the axial hole and therefore the passage between a chamberupstream and a chamber downstream from the plunger in the body when theplunger is in a first rest position and that the stem valve leaves thehole substantially open when the plunger is in the other position, and

c. a control aperture for the admission of a control pressure to areaction surface on the plunger in order to produce a regulable increasein the resistance offered by the resilient means to the movement of theplunger.

Further objects, advantages and features of the invention will be madeclear by the following particular description, given by way of example,of a preferred embodiment of the invention and a way of using thisembodiment, with reference to the accompanying drawings, in which FIG. 1shows a preferred embodiment of a pressure reducing valve in accordancewith the invention, in axial section, and

FIG. 2 very diagrammatically illustrates the pneumatic circuit of abraking installation which applies braking correction and in which areducing valve in accordance with the invention is incorporated.

With reference to FIG. 1, a pressure reducing valve in accordance withthe invention comprises a substantially cylindrical body having an axialhole in which a plunger slides; the plunger consists of two parts 11 and12 secured to one another by screws 13; a seal 11a is interposed betweenthe two parts. An axial hole 14 extends through the part 11. The strokeof the plunger 1 l, 12 is limited by a shoulder 15. Suitable O-ringseals 16 ensure pressure tightness between the circuit above and thecircuit below the plunger 11, 12. Pressure enters the valve through anaxial hole 17 extending through a top cover 18 secured by screws 19; anO-ring seal 20 is interposed between the cover and the body; pressureleaves the valve through a radial hole 21. A bottom wall 23 is alsoattached by screws 24, and an O- ring is interposed between the wall andthe body; a further passage 22 in this wall is used for rapid dischargeof the pressure in an operating cylinder not shown in the drawing, whichis downstream from the outlet 21. A valve 26 with a stem is movable inthe axial hole 14 of the plunger 11, 12 and is provided with two heads;one head 27 is secured to the stem by a screw 31 and a sealing O-ring 33is interposed between the head and the stem; this head is adapted tobear against a seat at the top end of the axial aperture 14 of theplunger 11, 12 so as to close this aperture; the other head 28 providedwith an O-ring 29 is adapted to bear against a seat formed in the top ofthe rapid discharge aperture 22. A resisting spring 30 is used forresisting the downward movement of the plunger 11, 12, and a centeringspring 31 is used for centering the stem valve 26 with respect to theplunger 11, 12. A control aperture 32 extends through the peripheralwall of the body 10; the presence of an annular channel 34 formed in thetop surface of the shoulder 15 permits a control pressure to reach thereaction section 36 on the plunger 1 1 12 through this inlet.

An outlet 35 at the bottom edge of the shoulder 15 permits the escape ofthe air contained between the plunger 1 1, 12 and the shoulder 15.

In the absence of delivery pressure from the inlet 17, the plunger 11,12 is raised by the resisting spring 30 and is in contact with the tophead 27 of the stem valve 26. The rapid discharge outlet 22 is open. Forthe moment it is assumed that there is no control pressure in theaperture 32. When. incoming pressure arrives through the inlet 17, thepressure acts on the plunger 11, 12 and on the stem valve 26, forcingthe unit as a whole downwards until the bottom head 28 of the stem valvebears against the seat in the rapid discharge aperture 22, whereas theplunger continues to descend and finally bears against the shoulder 15,so that the passage for the delivery pressure to the outlet 21 is openedand pressure is delivered to the operating cylinder not shown in thedrawing. When the incoming pressure ceases, the plunger 11,12 risesunder the action of the resisting spring 30 and the pressure downstreamfrom the outlet 21 so that the seat in the axial hole 14 in the plunger11,12 bears against the top head 27 of the stern valve 26 and at thesame time the rapid discharge aperture 22 is opened. The downstreampressure is therefore rapidly discharged through the rapid dischargeaperture 22. The discharge continues so long as the incoming pressureremains less than the force exerted by the downstream pressure and bythe resisting spring 30. The discharge is divided so as on the averageto satisfy the relationship P F= n.4,

(friction forces, which are practically negligible, are ignored). Here,P.) is the outgoing pressure or pressure downstream from the plunger 1l, 12, P, is the incoming or delivery pressure, A is the total area onwhich the incoming pressure acts, A is the area of the plunger on whichthe downstream pressure acts and F is the reaction force of theresisting spring. The downstream pressure is therefore PHAZ A, F: PA,

It is thus possible to control the reduction ratio between the incomingpressure and the outgoing pressure of the valve additively by means of acontrol pressure, with a control range which depends on the sizes of thearea A,, A and A A possible use of the pressure reducing valve of theinvention for braking correction in regard to load in an automobilebraking installation will now be described with reference to FIG. 2. InFIG. 2 the pressure reducing valve of the invention is showndiagrammatically at 40. Pressure from a master cylinder is appliedthrough a duct 41, and the outgoing pressure is transmitted to a brakecylinder 43 through an outlet 42. 44 indicates a cylinder pivoted at 45to a point on the frame 46; a plunger 47 slides in this cylinder againstthe reaction of the air contained in the cylinder, and a rod 48 of theplunger 47 is connected at 49 to an axle of the vehicle. When thepressure in the cylinder 44 falls below the adjusted value as a resultof losses and leakage, a nonreturn valve 51 for compensating theadjustment, which is subjected to the action of a spring, establishescommunication between a service reservoir (not shown in the drawing) andthe cylinder 44 through ajunction 52 and thus returns the said pressureto the adjusted value at each instant. An increase in the load on thevehicle causes the frame 46 to move towards the axle 49, thus reducingthe pressure in the cylinder 44 and therefore the pressure applied tothe control inlet 50 of the pressure reducing valve of the invention.

The relationship 1) shows that the pressure P transmitted to the powerdevice increases when the control pressure P decreases and thereforewhen the load carried by the vehicle increases. The braking action willtherefore be stronger when this load is greater.

Another possible use of the invention, not shown in the drawings,consists in employing the reducing valve of the invention as a pressurelimiting valve. In this case the control pressure will be the outgoingpressure itself,

ap ropriately a plied to the control inlet.

her lmpo ant uses of the invention are described in applicantsco-sending patent application Ser. No. 110,232 filed Jan. 27, 1971.

What we claim is:

l. A pressure reducing valve comprising a hollow cylinder having aninlet port, an outlet port, an exhaust port and a control port; aplunger having two flanges at opposite ends of an intermediate reduceddiameter portion an an axial bore extending through the flanges and thereduced diameter portion, said plunger being slidable in the hollowcylinder between a first position and a second position, one flange ofthe plunger definingan inlet chamber with the wall of said cylinder ad-2 jacent the inlet port and the opposite flange defining an outletchamber with the wall of said cylinder adjacent the outlet and exhaustports; said cylinder having an internal annular shoulder disposedbetween the flanges of said plunger, said shoulder having an annulargroove facing the side of said one flange opposite said inlet chamberand means communicating said groove with the control port; resilientmeans disposed in said outlet chamber biasing said plunger to said firstposition where said opposite flange rests against said shoulder; atwo-headed stem valve movably mounted in said axial bore of the plunger,spring means biasing one head of the stem valve into engagement withsaid exhaust port to close said exhaust port when said plunger is insaid second position, the other head of said stern valve being arrangedto cooperate with the axial bore in said one flange whereby said axialbore will be open when said plunger is disposed in said second positionand whereby when said plunger is disposed in said first position, saidone head of said stem valve will open said exhaust port and the otherhead of said stem valve will close said axial bore; said plunger beingshiftable from said first position to said second position where saidone flange rests against said shoulder when a pressure in said inletchamber exerts a force on said plunger exceeding the combined force ofthe pressure in said control port, the pressure in said outlet chamberand the force of said resilient means.

1. A pressure reducing valve comprising a hollow cylinder having aninlet port, an outlet port, an exhaust port and a control port; aplunger having two flanges at opposite ends of an intermediate reduceddiameter portion an an axial bore extending through the flanges and thereduced diameter portion, said plunger being slidable in the hollowcylinder between a first position and a second position, one flange ofthe plunger defining an inlet chamber with the wall of said cylinderadjacent the inlet port and the opposite flange defining an outletchamber with the wall of said cylinder adjacent the outlet and exhaustports; said cylinder having an internal annular shoulder disposedbetween the flanges of said plunger, said shoulder having an annulargroove facing the side of said one flange opposite said inlet chamberand means communicating said groove with the control port; resilientmeans disposed in said outlet chamber biasing Said plunger to said firstposition where said opposite flange rests against said shoulder; atwo-headed stem valve movably mounted in said axial bore of the plunger,spring means biasing one head of the stem valve into engagement withsaid exhaust port to close said exhaust port when said plunger is insaid second position, the other head of said stem valve being arrangedto cooperate with the axial bore in said one flange whereby said axialbore will be open when said plunger is disposed in said second positionand whereby when said plunger is disposed in said first position, saidone head of said stem valve will open said exhaust port and the otherhead of said stem valve will close said axial bore; said plunger beingshiftable from said first position to said second position where saidone flange rests against said shoulder when a pressure in said inletchamber exerts a force on said plunger exceeding the combined force ofthe pressure in said control port, the pressure in said outlet chamberand the force of said resilient means.